A metal-air battery is a battery, wherein redox reaction of oxygen as the cathode active material is carried out in the cathode, and redox reaction of a metal constituting the anode is carried out in the anode; thereby charge and/or discharge can be performed. The metal-air battery shows high energy density and enables downsizing easily so that it has attracted attention as a higher-capacity secondary battery superior to the conventional lithium-ion secondary battery. However, the metal-air battery is still problematic as a secondary battery and has many other problems which are raised by increasing the size of the battery itself for applying to automobiles.
For example, at charging and discharging of the metal-air battery, gas generates inside the battery. This is attributed to the above-described redox reaction, decomposition of the electrolyte, and so on. The gas is supposed to give negative effects to the cell reaction; therefore, means for inhibiting generation of the gas inside the battery and means for discharge the gas inside the battery have been proposed.
For instance, to inhibit generation of gas between an air electrode and an electrolyte, Patent document 1 proposes to raise concentration of active material showing higher oxygen generation potential at the electrolyte side of the electrode. In addition, Patent document 2 discloses an art to produce an air battery comprising gas collection regions and gas discharge pores in a battery case to discharge the gas produced in the battery case. Moreover, Patent document 3 proposes an aluminum-air solid battery characterized in that: an anode and a plurality of cathodes are connected through a solid electrolyte; the anode is made of aluminum or an aluminum alloy; the cathode is made by a plurality of air electrodes; and the anode, the plurality of cathode, and the solid electrolyte are laminated at least a part of the battery.    Patent Document 1: Published Japanese translations of PCT application No. 08-504998    Patent Document 2: Published Japanese translations of PCT application No. 09-500480    Patent Document 3: Japanese Patent Application Laid-Open (JP-A) No. 2006-190522